RESUMO
Heavy metals, such as Fe, Zn, and Cd, are major pollutants in aquatic ecosystems. These toxicants usually are present in these ecosystems in the form of mixtures, and their effect on exposed organisms is the result of interactions occurring between the metals as well as with other pollutants and environmental factors. The present study evaluated the uptake of Cd, Fe, and Zn individually and as a mixture and their effect on adenosine triphosphate (ATP) content in Limnodrillus hoffmeisteri, an important aquatic organism given its resistance to large amounts of these xenobiotics. Test organisms were exposed for 96 h to sediment treated with each of these metals individually and as a mixture. The metal concentrations used were equivalent to the zero lethal concentration of these pollutants as determined in a previous study. At the end of the exposure period, metal concentration in medium and organism as well as ATP content in the latter were quantified. Metal uptake was measured by determining the bioconcentration factor at 96 h. All three metals elicited an important decrease in ATP content when acting singly and as part of a mixture. When present as a mixture, their uptake and effect on L. hoffmeisteri are modified. Therefore, a joint-action toxicity approach should be used for toxicity evaluations involving these pollutants.
